Project Summary In 2014, approximately 6 million Americans with diabetes were living with the accompanying condition diabetic retinopathy, which is the largest cause of blindness among working-age individuals in the United States. During the progression of DR, ischemic neuronal cells in the retina begin to express vascular endothelial growth factor-A (VEGF-A), leading to macular edema and retinal neovascularization. Inhibition of VEGF-A has become an important approach to ameliorate the sequelae of DR, though current anti-VEGF drugs are rapidly cleared from the vitreous and require frequent administration by intravitreal injection to maintain an effective treatment concentration. Valitor, Inc. is developing protein-polymer therapeutics to overcome the vision- threatening effects of DR. As one example of our patented technology platform, we have conjugated soluble VEGF receptor-1 (sFlt) to linear chains of the natural biopolymer hyaluronic acid (HyA) to generate multivalent conjugates of sFlt (mvsFlt) that are substantially larger than any drugs currently delivered by intravitreal injection. Increasing the size of the mvsFlt conjugates will substantially reduce their clearance rate out of the vitreous, and we have preliminary evidence that mvsFlt conjugates retained within eye can effectively antagonize VEGF-A signaling in the retina, where the VEGF-induced pathologies associated with DR occur. We have designed our mvsFlt therapy to provide sustained anti-VEGF bioactivity following administration by intravitreal injection, which will allow for effective therapy with less frequent treatment sessions. Thus, our strategy for sustained anti-VEGF therapy has the potential to improve both the safety and cost efficacy of DR treatment. Our Phase I objective is to demonstrate that increasing the macromolecular size of mvsFlt conjugates will increase the duration of effective DR treatment. In Specific Aim 1, we will determine how mvsFlt size will affect both its localization within the eye and its ability to provide sustained anti-VEGF therapy. In Specific Aim 2, we will determine the intravitreal half-life of mvsFlt conjugates using a model that will allow direct comparison to published data for clinically available anti-VEGF drugs. Our findings will provide valuable proof-of-mechanism data for further pre-clinical development of our drug product, which we have planned for Phase II of this project.